linux-kernel - Re: Non-random RDRAND Re: [PATCH] x86/CPU/AMD: Clear RDRAND CPUID bit on AMD family 15h/16h

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Date:   Fri, 16 Aug 2019 10:42:45 -0400
From:   Neil Horman <nhorman@...driver.com>
To:     "Theodore Y. Ts'o" <tytso@....edu>, Pavel Machek <pavel@....cz>,
        "Lendacky, Thomas" <Thomas.Lendacky@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Chen Yu <yu.c.chen@...el.com>, Jonathan Corbet <corbet@....net>
Subject: Re: Non-random RDRAND Re: [PATCH] x86/CPU/AMD: Clear RDRAND CPUID
 bit on AMD family 15h/16h

On Thu, Aug 15, 2019 at 11:12:24AM -0400, Theodore Y. Ts'o wrote:
> On Thu, Aug 15, 2019 at 01:24:35AM +0200, Pavel Machek wrote:
> > Burn it with fire!
> > 
> > I mean... people were afraid RDRAND would be backdoored, and you now
> > confirm ... it indeed _is_ backdoored? /., here's news for you!
> 
> To be fair to AMD, I wouldn't call it a backdoor.  Hanlon's razor is
> applicable here:
> 
> 	"Never attribute to malice that which can be adequately
> 	explained by neglect."
> 
> (Sometimes other words are used instead of neglect, but i'm trying to
> be nice.)
> 
Is it worth setting up a quirk for the Excavator era cpus, that triggers
a call to rdseed on resume?  Working under the assumption that calling
rdseed would kick the rdrand instruction back into gear.

Neil

> 
> 					- Ted
> 
> P.S.   Also applicable:
> 
> 	https://www.youtube.com/watch?v=XZxzJGgox_E
>